The emerging field of molecular electronics holds the promise for ultimate miniaturization of computer memory and logic circuits down to nanometer size. At nanoscale dimensions, electronic circuit elements cannot be fabricated by conventional photolithographic methods, as is well-known. Moreover, the conventional principles of transporting, amplifying, and switching currents do not work anymore. Molecular electronics (moletronics) has to provide molecular-size replacements for various elements of semiconductor electronics.
Traditionally, moletronic solutions have been focused on finding single-molecule wires, diodes, switches, transistors, and so on, that are on elements that could perform single electronic functions. However, most of memory and logic designs require combinations of two or more functions being performed simultaneously. For instance, a viable crossbar memory architecture contains a combination of a switch and a diode in series connection at every bit (crossbar junction). The same diode-switch combination is a necessary element for reconfigurable computer logic architectures.
Previously, the creation of such a combination was perceived to be simple addition. For instance, one could use two molecular layers, wherein one layer would contain switches and another layer diodes. However, this would make the device fabrication more difficult. More importantly, in such a design, one molecular layer is likely to interfere with another, which may spoil useful electronic properties of both layers. The device becomes more faulty, less reliable, and more expensive to build.
Thus, there is a need to provide circuit elements that utilize a single molecular species. In particular, there is a need to provide single molecular species that can perform more than one function.